Coloration of metallic surfaces



Italy, residing at Turin UNITED s'rA'ras PATENT 'rrro RONDELLI, orrunm,ann eumino sns'rmr, or ammo,- ITALY, assron'oas or onn-rnmn 'rosnsrnon (FOREIGN PATENTS) LIMITED, or LONDON, rum

LAND.

comm'rron or METALLIC sunraons.

No Drawing.

To all whom it may concern:

Be it known that we, Trro RQNDELLI and QUIRINO Snsrmr, subjects of theKin of Italy, and er'-' game, Italy, respectively, have lnvented certainnew and useful Improvements in the Coloration of Metallic Surfaces, (forwhich on October 27, 1916, we filed an application No. 156,509 forLetters Patent of Italy), ofwhich the following is a specification.

This invention relates to the coloration of metallic surfaces, and hasfor its object to provide an improved process for this purose. p In theprior British specification, No. 106774 (No. 16582/16) a process forbronzing or colouring metallic surfaces is described according to whichthe surface to be bronzed or coloured is electrolytically coated withcopper from an electrolyte which is ahot dense alkaline solution, (forexample, having a temperature of v about 120140 C and adensity about1.3-1.5)

containing an oxide of copper combined.

with the alkali, and the surface is then coloured or bronzed, forexample, by anodic oxidation in the electrolytic bath. It has now beenfound that a modification of this process is specially adaptable for thecoloration of metallic surfaces, such as copper and ferrous surfaces.

According to the present invention the improved process for colouringmetallic surfaces consists in immersing the object, the surface of whichis to be coloured, in a warm or hot electrol ic bath containing a Kfixedalkali in which 1s dissolved, preferably to saturation or substantiallyso, a compound of copper, for example, oupric oxide or hydrate, theobject under treatment being made to serve exclusively as anode for a.shorter or longer period.

a The copper bath may be prepared in any suitable way by chemlcal orGlBCtI'O-ChBlllb 1920. Serial No. 393,198.

preferably is such that the solution boils at a comparatively hightemperature, for,

example 120150 C. A wide range of cur- Patented May as, recap rentdensity is applicable, for instance,

from 1-30 amperes per square decimeter of the surface to be coloured,the particular density employed depending, of course, upon thecircumstances of the case. For certain copper alloys it will be foundthat a comparatively low current density should be used, such as onefrom 3-5 amperes per s uare decimeter, while in other cases, as w en thesurface under treatment consists ofsubstantially pure copper or ofbronze of-high copper content, a density of from l0-12 amperes may beconveniently employed. As will be readily understood, the conditions inany given case will be de termined'b the nature of the surface to becoloure the object and the particular effect desired. The sameconsiderations apply to the "tem perature and to the time during whichthe object is immersed. When copper alloys are in question theconcentration of the bath as well as by the nature of and thetemperature depend in particular upon the constitution of the alloy. Inevery case, however, a simple preliminary experiment sufiices todetermine the most ad-' vantageous conditions necessary to obtain theresult desired. By varyin the conditions different effects, from fightgreen and dark blue colours through darker colorations u to black, maybe produced, I

.The f0 lowing'examples will serve to indicate the character of theinvention in more detail, but it is to be understood that these examplesare given as illustrative only and not by wayof limitation.

Example 'I. v Copper oxide is dissolved to saturation'in a solution ofcaustic soda which boils bea 'duced.

sistant to corrosive agencies and can be .pol-

the anode in the same bath as in Example 1,. under current density of 5amperes per square decimeter, the temperature being 75 and the time ofimmersion about 2 minutes. A similar result is obtained as in theprevious case;- If the treatment be applied only for afew secondsiridescent effects are pro- Ewample 111. An.iron object is immersed inthe same 'bath as in the previous examples, the temperature beingbetween 90-1309; and is subsulphides or sulphides of alkali earths, and

mitted to anodic-oxidation under a current density not exceeding 5amperes per square decimeter. After about 5-20 minutes treatment,according to the constitution of the iron, and-the condition of thesurface, the latter is coloured a deep blue black.

Not infrequently, copper and copper alloy surfaces are coloured bydeposition thereon of arsenic, or even, in some cases, of platinum, bfutcoloration is more generally effected by treatment in solutions ofalkali it. has also been the practice to employ a solution of coppernitrate, or of copper. carbonatein ammonia. The three first processes,however, do not give satisfactory results either in respect to thecolour produced, or to its: permanence, while the last two methods arenot easy of application, and regular effects are difficult to obtain.The present invention provides a simple and expeditious means ofcolouring metallic surfaces, and of obtaining varied effects withfacility and regularity.

A process for oxidizing ferrous surfaces by treating the same withoutthe use of an electric current in an alkaline bath containing the oxideof a metal which behaves electro-negatively towards iron is describedand. claimed in our co-pending application Serial No. 393,199, filedJune 30, 1920.

What we claim as our invent-ion and desire to secure by Letters Patentis 1. The process for colouring metallic surfaces which comprisessubmitting the surface to be coloured to anodic oxidation in thepresence of a. concentrated alkaline electrolyte containing copper.

2. The process for colouring metallic surfaces which comprises immersingthe object the surface of which is to be coloured in a concentratedsolution of fixed alkali in which is dissolved a compound of copper andsubmitting the surface to anodic oxidation.

. 3. The process for colouring metallic surfaces which comprisesimmersing the object the surface of which is to be coloured in aconcentrated solution'of fixed alkali in which is dissolved a compoundof copper and submitting the surface to anodic oxidation withapplication of heat.

4. The process for colouring metallic surfaceswhich comprises immersingthe objectthe surface of which is to be coloured in a concentratedsolution of fixed alkali in which is dissolved to saturation a. compoundof copper and submitting the surface toanodic oxldation. A y

5. The p-rocessfor colouring metallic surfaces which comprises immersingthe object the surface of which is to be coloured in a solution offixedalkali of a densit of 1.3-1.5 in which is dissolved a compound andsubmitting the surface toanodic oxida- 6. The process for colouringmetallic surof copper faces which comprises immersing the object v thesurface of which is to be coloured in a solution'of caustic alkali of adensity of 1.3-1.5 in which is dissolved a compound of copper andsubmitting the surfacetoanodic oxidation. p

7; The process for colouring metallic surfaces which comprises immersingthe object the surface of which is to be coloured in a solution ofcaustic soda of a density of 1.3-1.5 in which copper oxide is dissolvedto saturation and submitting the surface to anodic oxidation.

'8. The process for colouring metallic surfaces which comprisesimmersing the object the surface of Which is to be coloured in a.

solution of caustic soda of a density of 1.3-1.5 in which copper oxideis dissolved to saturation and submitting the surface to anodicoxidation with application of heat.

9. The process for colouring a copper. surface which comprises immersingthe object the surface of which is to be coloured in a concentratedsolution of fixed alkali in which is dissolved a compound of copper andsubmitting the surface to anodic oxidation.

10. The process for colouring a copper S111. face which comprisesimmersing the object the surface of which is to be coloured in asolution of caustic soda, having a boilingpoint between about 120130, inwhich copper oxide is dissolved to saturation and submitting the surfaceto anodic oxidation with application of heat.

In testimony whereof we have signed our names to this specification inthe presence of twosubscribing witnesses.

1 TITO RO-NDELLI.

QUIRINOv SES-TINI.

Witnesses to signature of Trro RoNDELLI:

J. PHILLIPS CRAWLEY, J. W. PATCHING. Witnesses to signature of QUIRINOSnsrrm:

DANTE DANIELE, Anselmo Vnm',

